Geophys. J. Int. (2009) 177, 691–716 doi: 10.1111/j.1365-246X.2008.04059.x Glacial rebound and plate spreading: results from the first countrywide GPS observations in Iceland ∗ T. Arnad´ ottir,´ 1 B. Lund,2 W. Jiang,1 H. Geirsson,3 H. Bjornsson,¨ 4 P. Einarsson4 and T. Sigurdsson5 1Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjav´ık, Iceland. E-mail:
[email protected] 2Department of Earth Sciences, Uppsala University, Villavagen¨ 16, 752 36 Uppsala, Sweden 3Physics Department, Icelandic Meteorological Office, Reykjav´ık, Iceland 4Institute of Earth Sciences, University of Iceland, IS-101 Reykjav´ık, Iceland 5National Land Survey of Iceland, Akranes, Iceland Downloaded from https://academic.oup.com/gji/article/177/2/691/2023257 by guest on 30 September 2021 Accepted 2008 December 10. Received 2008 December 5; in original form 2008 June 12 SUMMARY Iceland is one of the few places on Earth where a divergent plate boundary can be observed on land. Direct observations of crustal deformation for the whole country are available for the first time from nationwide Global Positioning System (GPS) campaigns in 1993 and 2004. The plate spreading across the island is imaged by the horizontal velocity field and high uplift rates (≥10 mm yr−1) are observed over a large part of central and southeastern Iceland. Several earthquakes, volcanic intrusions and eruptions occurred during the time spanned by the measurements, causing local disturbances of the deformation field. After correcting for the largest earthquakes during the observation period, we calculate the strain rate field and find that the main feature of the field is the extension across the rift zones, subparallel to the direction of plate motion.